Study of γ ray emission of supernova remnants interacting with molecular clouds and optimization of H.E.S.S. data analysis

The H.E.S.S. experiment is an array of Cherenkov telescopes, located in Namibia, observing the very high energy γ rays from astrophysical sources. H.E.S.S. greatly increased our understanding of the very high energy non thermal universe. Since 2012, a fifth telescope was installed at the center of the array. This improvement increase the energy range and the sensitivity of the detector. The optimization of a multivariate analysis method, within the H.E.S.S. framework, is presented in this thesis. The X_eff analysis is improved by taking into account the observation conditions and by increasing the number of discriminating variables. The sensitivity of this analysis compared to standard analyses is demonstrated. X_eff is then used to analyze several sources of γ rays. The effects of the focus impacting the H.E.S.S. II data are described. They are taken into account in the analysis and an optimization of the distance between the mirrors and the camera is presented. The study of the γ emission from four candidates of molecular clouds and supernova remnant associations is presented. The H.E.S.S. data from G349.7+0.2,W51, the Tornado nebula and HESS J1745-303 is performed. The interpretation of their emission, using also Fermi-LAT data, leads to the estimation of the particles acceleration efficiency in these objects. The work described in this thesis led to the production of two internal notes in the H.E.S.S. collaboration, to several presentations in international conferences, and scientific publications. (author)